What would you guys recommend for a wireless system? I am going to shoot a wedding in a few months, and also have some random stuff lined up, such as dentist office/doctor/etc. I have been looking at the Sennheiser G2 100 model.

In price vs features, the Sennheiser G2 system wins. If you can afford to spend more (perhaps a lot more), Lectrosonics is the industry standard. I have a Sennheiser system and love it. I have only had minor static in an 80x100 foot room filled with about 100-200 people with cellphones on. Very good for a sub $1,000 system.

What kit do you recommend? I am looking at the $550 kit, but I am confused at what the $699 kit has to offer. There is some xlr wireless transmitter... Or I think that is what it is. Does this then allow you to use a condensor mic or a mic that needs powered?

The XLR plug-on transmitter is for turning any XLR handheld or shotgun mic into a wireless mic. The G2 100 series doesn't provide phantom power, but the G2 500 series does.
The difference between the M2 and M4 I believe is the pickup pattern. One is omni and one is cardioid.

Steve... I've been following your thread since I'm also interested in getting a new mic set. One question, what kind of a camera mount do you use with the Sennheiser receiver? Or does the receiver have a built-in mount. I would favor a shoe mount that permits the receiver to lie flat on the camera rather that stick up.

I used my Sennheiser wireless omni a week ago on a ballroom dance instructor. My wife had cautioned me against using the mic on a silk tie. Sure enough any movement caused the tie to rustle and the mic would pick it up.

Otherwise the mic worked extremely well. Very strong signal with no dropouts.

What kind of a camera mount do you use with the Sennheiser receiver? Thanks, Bob

I have a system that I have used for years. Really cheap and can easily be moved from camera to camera, if necessary. Industrial strength Velcro. I have often piggy backed receivers this way. I have never had one fall off yet. If you have to swap batteries or recievers, it makes them really easy to service. Of course, back in the day of BetaCams it was a lot easier to find a suitable flat surface to stick the Velcro to.